1. Field of the Invention
The present invention relates to a band saw and more specifically, to a device for guiding a saw blade of the band saw.
2. Description of the Related Art
A conventional band saw generally uses a saw blade guiding device to guide movement of the saw blade. FIG. 1 shows a saw blade guiding device 70 according to the prior art. According to this design, the saw blade guiding device 70 comprises a mounting base 71 affixed to a lifting mechanism of a band saw (not shown), a saw blade urging unit 72 provided at the front side of the mounting base 71 near the top, and a saw blade guiding unit 73 provided at the front side of the mounting base 71 near the bottom. The saw blade urging unit 72 comprises a shaft 722 fixedly connected to the mounting base 71, and a roller 724 rotatably supported on the shaft 722 and disposed in contact with the back side of the saw blade 74 opposite to the cutting teeth of the saw blade 74. The saw blade guiding unit 73 comprises a wheel holder 731 affixed to the mounting base 72, two screw bolts 732 fastened to the wheel holder 731 and arranged in parallel, and two rollers 733 respectively rotatably supported on the screw bolts 732 and disposed in contact with the two opposite lateral sides of the saw blade 74.
The aforesaid conventional saw blade guiding device 70 is still not satisfactory in function because of the following drawbacks:
1. The rollers 724 and 733 are directly contacted with the saw blade 74. When the saw blade 74 is driven to move by the motor (not shown), a friction is produced between the saw blade 74 and the rollers 724 and 733. Because the rollers 724 and 733 are metal members, the surfaces of the rollers 724 and 733 might wear out quickly with the use of the metal rollers 724 and 733. Further, during friction contact between the saw blade 74 and the metal rollers 724 and 733, noise in high level will be produced.
2. When the surfaces of the rollers 724 and 733 start to wear, the rollers 724 and 733 will be unable to prohibit the saw blade 74 from biasing during cutting working, thereby resulting in a poor cutting quality.